Heat exchangers and methods of making the same



1961 L. E. GIBBS 2,995,807

HEAT EXCHANGERS AND METHODS OF MAKING THE SAME Filed Nov. 29, 1957 2 Sheets-Sheet 1 E19 1. A 4A I a ""1 l il a Imam.- 5 L'eZandE 6125450,

Aug. 15, 1961 E. GIBBS 2,995,807

HEAT EXCHANGERS AND METHODS OF MAKING THE SAME Filed Nov. 29, 1957 2 Sheets-Sheet 2 United States Patent 2,995,807 HEAT EXCHANGERS AND METHODS OF MAKING THE SAME Leland E. Gibbs, ome, N.Y., assignor to lRevere Copper and Brass Incorporated, Rome, N.Y., a corporation of Maryland Filed Nov. 29, 1957, Ser. No. 699,769 Claims. (Cl. 29-'157.3)

My invention relates to heat exchangers of the type having a wall, of relatively thin heat conductive sheet metal, with which is associated one or more conduits, in heat conductive relation to the wall, for passage therethrough of a heating or cooling medium.

According to the present invention, the wall is substantially endless so as to enclose a space which, or material contained therein, is to be heated or refrigerated by a medium passing through the conduit or conduits associated with the wall. For example, the wall may constitute the lining of the quick freezing compartment of a domestic refrigerator, or the lining of a receptacle for containing water to be cooled or heated by a refrigerant or heating medium passed through the conduit or conduits. In instances where the wall is associated with say two conduits both may conduct the same refrigerant or heating medium or one may conduct a different refrigerant or heating medium from the one conducted by the other, or one may be used at times to conduct a refrigerant and the other at other times a heating medium, or one may be used to conduct a refrigerant or heating medium and the other a fluid which is to be heated or cooled by conduction through the metal of the wall from one conduit to the other.

Such walls have heretofore been made by bending a sheet of thin heat conductive metal to the desired shape, usually rectangular or cylindrical, and attaching by brazing or otherwise to the inner or outer surface of the sheet constituting the wall a helical tube, of heat conductive metal, the turns of which extend about the wall in contact therewith. Such construction, however, is expensive by reason of the material and labor costs involved in producing it, and has the defect of requiring the conduction of heat through the brazing material conheating the tube to the wall.

It is an object of the present invention to secure a less expensive construction and eliminate the necessity of attaching to the sheet metal constituting the wall the conduit which conducts the heating medium or refrigerant.

The invention, however, will be best understood from the following description when read in the light of the accompanying drawings of several embodiments of the invention selected for illustrative purposes, while the scope of the invention will be more particularly pointed out in the appended claims.

In the drawings:

.FIG. 1 is an explanatory diagram of a step in one form of the method according to the invention;

FIG. 2 is an explanatory diagram of a further step in the method;

FIG. 3 is an isometric view of one form of heat exchanger, according to the invention, produced by the method comprising the steps indicated by FIGS. 1 and '2;

FIG. 4 illustrates the cross-sectional shape of a sheet employed in making the heat exchanger according to F18. 3, .and corresponds to a section on the line 4-4 .of F1 1;

FIG. 5 is a section on the line 5-5 of FIG. 3;

FIG. 6 is a section on the line 6-6 of FIG. 2;

FIGS. 7 to 10 illustrate steps which may be employed for connecting, to the partially completed heat exchanger,

nipples or the like for conducting-the heating medium or 2,995,807 Patented Aug. 15, 1961 refrigerant to and from the conduit of the completed heat exchanger; and

FIGS. 11 and 12. are explanatory diagrams of steps in the method of making a modified form of heat exchanger.

Referring to FIGS. 3 and 5 of the drawings, the heat exchanger may comprise a heat conductive metal sheet 1 bent to a rectangular shape to form the longitudinally extending walls 3 and 5 and end walls 7 and 9, the opposite end edges 11 and 13 of the sheet being placed in face abutting relation and joined together by suitable means such as welding or brazing. Extending about the four walls of the heat exchanger helically, as shown in FIG. 3, is a tubular conduit 15 which, starting from and ending at the abutting end edges of the original sheet, has, as shown, the spaced turns 17, 19, 2A1 and 23.

As further shown, the two terminals of the coiled conduit 15 are each provided .with a nipple 25, through one of which nipples heating medium or refrigerant may be entered into the conduit and through the other of which such medium or refrigerant may be discharged therefrom.

Preferably, and as best shown in FIG. 5, the opposite walls 27 of the tubular conduit :15 are integral with the metal of the sheet 1, in other words, the tubular conduit is seamless and is connected at diametrically opposite sides thereof to the metal of the sheet by seamless joints, there being an entire absence of welded, brazed or other joints longitudinally of the conduit except where the opposite edges 11 and 13 of the original sheet abut each other and are there joined together, such abutting edges in the finished product illustrated including the abutting ends of the turns of the tubular conduit.

In making the heat exchanger illustrated there may be employed, as a starting material, a thin gauge sheet 29 (FIGS. 1 and 4) of cold workable heat conductive metal, such as copper, aluminum, or the like, and of requisite length to be bent to form the heat exchanger according to FIG. 3, said sheet having between its opposite faces and side edges a row of parallel slits 3d, 33, 35 and 37 extending throughout its length, the exact number of slits in this row depending upon the number of turns which the tubular conduit 15 of FIG. 3 is to have. This sheet may be formed of lengths cut from a very much longer sheet produced by any of the methods disclosed in copending applications of Richard A. Wilkins, Serial Number 518,768, filed June 29, 1955, and Serial Number 570,372, filed March 8, 1956. Such methods may comprise casting the metal of a relatively thick billet about a row of spaced elongated pulverizable rods or the like extending lengthwise of the billet, and then rolling the billet for thinning it and elongating it in the direction of the lengths of the rods, such rolling moving the opposite sides of the spaces occupied by the rods into close proximity to form the slits, and crushing the rods to a fine weld preventing powder which is spread along said spaces and slits as the billet is being so thinned and elongated to form a thin gauge strip or sheet. The elongated rods or pulverizable members may be of various materials as, for example, when the sheet is of copper may be of graphite, and when of aluminum may be of soapstone. The residual layer of weld preventing powder in the slits will be in the form of an attenuated film commonly in the order of about 0.0001 inch in thickness, the powder adhering to the walls of the slits. This film on a much magnified scale is indicated at 39 in FIG. 6. These slits may be inflated, by introducing pressure fluid into them, to form tubular passages.

The sheet 29 may be cut, as diagrammatically indicated in FIG. 1, on an angle to the lengths of the slits to form the rectangular sheet 41 of suificient length .to be bent to the shape of the sheet 1 of FIG. 3, the sheet 3 41 having the opposite end edges 11 and 13. The sheet 41 may then be bent along lines parallel to the end edges 11 and 13 to bring those edges into abutting relation and form walls corresponding to the walls 3, 5, 7 and 9 of the heat exchanger shown by FIG. 3. As diagrammatically indicated in FIG. 2, when the sheet 41 is so bent the left hand end of the slit 31 of such sheet will be brought into registry with the right hand end of the slit 33, the left hand end of the slit 33 into registry with the right hand end of the slit 35, and the left hand end of the slit 35 into registry with the right hand end of the slit 37, to form a longer slit extending helically around the continuous wall formed by such bending, the upper end of the helix being formed by the right hand end of the slit 31 as viewed in FIG. 1, and the lower end of the helix being formed by the left hand end of the slit 37 as so viewed. After the edges 11 and 13 of the sheet 41 are brought into facing abutting relation, and before the slits are infiated, they may be joined together, for example, by welding as indicated at 42 (FIGS. 3 and 6). Such welding may be done, for example, by striking an are against the metal at the joint from a non-consumable electrode in an atmosphere of shielding gas. For such purpose an arc of requisite intensity may be caused to traverse the unslitted portions of the sheet at the joint first at one side of the sheet and then at its opposite side to fusion weld those portions together. Then an arc, of lesser intensity requisite to fusion weld together the thinner metal at the slitted portions of the sheet without unduly liquefya ing them, may be caused to traverse those portions at the joint first at one side of the sheet and then at its opposite side. The film 39 of weld preventing material in the slits at the joint will prevent the weld from extending across the slits and interrupting the continuity of the long helical slit. In fact the slight space between opposite faces of the slits formed by the film of weld preventing material will prevent the weld from so extending, it such film is removed from the slits adjacent the joint, if an arc of intensity suitable for the purpose is employed for welding the sheet at the slitted portions thereof.

After the abutting edges of the sheet 41 are joined together the nipples 25 may be attached. Conveniently this may be done by cutting away the sheet at-sides of the weld opposite the ends of the helical slit to form the slots, indicated at 43 (FIG. 7), to enable a suitable tool to' be presentedto each end of the slit and forced into it to expand it mechanically to form a socket-like opening 45 (FIG. 9) of circular transverse cross-section, whereupon the end of the nipple may be inserted through the slot 43 into such opening and brazed to the walls thereof. After the two nipples are brazed into place one may be temporarily plugged and the other connected to a source of pressure fluid for permanently expanding or inflating the slit to form the tubular conduit 15 of FIG. 3.

Also the ends of the passages may be joined, and,-if desired, without joining those portions of the facing end edges of the sheet which lie between said passages, by expanding to a cylindrical shape the end portions of the slits for a short distance inwardly of said end edges by use of a suitable tool, and inserting in such expanded portions before the slits are inflated the end portions of short connecting nipples which may be brazed in place, whereupon after the nipples 25 are attached the slits may be inflated in the way above explained. This expedient also may be employed when one of the slits, say the one lying next to one of the longitudinal side edges of the sheet, is wider than the rest of the slits, so as to form when the wider slit is inflated a passage'of greater diameter than is formed by inflation of the rest of the slits, the passage of greater diameter to serve for example as an accumulator for the refrigerant, in which case the connecting nipple joining the end of the wider slit to the adjacent end of the narrower slit will be a reducing nipple, that is to say, will have its end received in the expanded portion of the wider slit of greater diameter than its end received in the expanded portion of the narrower slit.

It will be understood that, although there would perhaps be in the ordinary case but little point in doing so, the ends of the helical slit may terminate short of the abutting edges of the. sheet, for example, at points corresponding to the line A-A (FIG. 2), at which places the nipples 25 may be connected to the ends of the conduit in the way hcreinbefore described. Also it will be understood that, again in the ordinary case with perhaps but little point in doing so, the ends of the sheet 41 may not be cut on a straight line. For example, they could be cut to' cause the joint between the ends of th sheet to coincide with the line B-B (FIG. 3), it being necessary' when the sheet 41 is bent to bring'its opposite end edges into contact only that the ends of the slits and the portions of said edges at opposite sides of them register-t9 formthe' elongated helical slit, 1 It will also be-understood that,although the sheet 41 may have asmany-slits as desired so, as to provide a helical coil of as many turns as desired, it may have but .two slits, namely, the slits 31 and 33 of FIGS. 1 and 2, the slits 35 and 37f0f those figures being omitted, in which case the helicalcoil of the heat exchanger will have but two turns.

I A heat exchanger, otherwise similar to the one above described, may be formed with a plurality of the helical coils,for example, two such coils as indicatedby the steps of the method diagrammatically illustrated by FIGS, 11 and 12. In this case the starting sheet 47 may have,-for example, eight slits, as indicated in F-IG. l 1, and be cut at such an angle to said slits as to form the rectangular sheet indicated at 49, the end edges 51 of the sheet}? being at such an angle to the slits that when the sheet is bent to form a continuous wall there will be formed two longer-helical slits onehaving -turns formed by the slits 53 and the other having turns formed by the slits 55. To the ends-of these helical slits so formed may be connected the nipples Z5 and the slits inflated to form two helical tubular conduits the turns of which are-parallel .to each other, with the turns of one positioned between the turns of the other.

It will be understood that within the scope of the appended claims wide deviations may be made from the forms of the invention herein, described without departing from the spirit of the invention. I claim: v

l. The method of forming a heat exchanger of the character described comprising providing an integral scarriless metal sheet Irolled from a cast'billet to have between its opposite faces and opposite side edges a row of at least two spaced slits extending longitudinally thereof, the-slit adjacent one side edge opening on at least one end edge of the sheet and the slit adjacent the other side edge opening on at least the opposite end edge, such other slits as may be included in said row opening on both end edges, correlating the spacing of the slits for bringing openings of slits of one sheet end edge intoalignment with openings of other slits at the other sheet end edge when the sheet is bent bending said sheet to form a circumferential wall in which opposite end edges of the sheet are in abutting relation with'the ends of different slits at said edges in registry and in such Wise that said slits collectively form one-or more longer continuous slits extending helically about said wall, said end edges being so shaped with relation to each other and the body of said sheet that when ends of the slits are in such registry said end edges will abut each other for the full widths of registering slits and also abut each other at at least those portions thereof which are contiguous with the opposite edges of registering slits, joining'said end edges together by welding or the like at their abutting portions between adjacent registering slits and at their portions between the faces of the 1 slits and thefaces of the sheet for the full widths of those portions, and after said end edges are so joined introducing pressure fluid into the so formed longer slits for expanding them to form tubular passages.

2. The method according to claim 1 in which the sheet provided is of rectangular shape with its edges at such angles to the slits that when the sheet is bent to form the enclosure wall and place the end edges of the sheet in abutting relation with the ends of the slits in registry said wall will be of uniform height throughout its extent.

3. The method according to claim 1 in which all the slits open at their opposite ends on the end edges of the sheet whereby one end of the slit adjacent each side edge of the sheet abuts against an unslitted portion of an end edge of the sheet, the metal at the ends of the slits between the faces of the slits and faces of the sheet at said unslitted portions being joined to those portions.

4. The method according to claim 1 in which the sheet provided is of rectangular shape with its edges at such angles to the slits that when the sheet is bent to form the enclosure wall and place the end edges of the sheet in abutting relation with the ends of the slits in registry said wall will be of uniform height throughout its extent, and in which all the slits open at their opposite ends on the end edges of the sheet whereby one end of the slits adjacent opposite side edges of the sheet abut against an unslitted portion of an end edge of the sheet, the metal at the ends of the slits between the faces of the slits and faces of the sheet at said unslitted portions being joined to those portions.

5. The method according to claim 1 in which the sheet provided is rectangular and has a row of at least four slits with the two adjacent slits next to each longitudinally extending side edge of the sheet opening on at least one end edge of the sheet, such other slits as may be included in the row opening on each end edge of the sheet, the end edges being at such angle to the slits that when the sheet is bent to place such end edges in abutting relation and form the enclosure wall ends of slits opening on said end edges will be placed in registry in such wise as to form a pair of longer slits extending helically about such wall with the turns of one helix positioned between the turns of the other helix.

References Cited in the file of this patent UNITED STATES PATENTS 2,289,685 Schoen July 14, 1942 2,595,472 Larkin May 6, 1952 2,626,130 Raskin Ian. 20, 1953 2,690,002 Grenell Sept. 28, 1954 2,712,736 Wurtz July 12, 1955 2,740,188 Simmons Apr. 3, 1956 2,766,019 Adams et a1. Oct. 9, 1956 2,766,514 Adams Oct. 16, 1956 2,779,086 Rieppel et a1. Jan. 29, 1957 2,856,162 Adams Oct. 14, 1958 

